As is well known, in polymerization type reactions, deposits or buildup of polymer occurs on the inner reactor surfaces which not only interferes with heat transfer, but decreases productivity and adversely affects polymer quality. This problem of buildup is particularly bad in the commercial production of polymers and copolymers of vinyl and vinylidene halides, when polymerized alone or with other vinylidene monomers having a terminal CH.sub.2 .dbd.CH&lt; group, or with polymerizable monoolefinic monomers. For example, in the commercial production of vinyl chloride polymers, the same are usually produced in the form of discrete particles by polymerizing in aqueous suspension systems. When employing such a polymerization system, the vinyl chloride and other comonomers when used, are maintained in the form of small discrete droplets by the use of suspending agents and agitation. When the reaction is complete, the resultant polymer is washed and dried. The reaction is usually conducted under pressure in metal reactors equipped with baffles and high speed agitators. However, these polymerization systems are, in many cases, unstable. As a consequence, polymer buildup forms on the interior surfaces of the polymerization reactor, including the surfaces of the baffles and agitator. Obviously this polymeric buildup must be removed due to the deleterious effect it causes, particularly on polymer quality.
Various methods have heretofore been proposed to reduce the amount and nature of polymer buildup on polymerization reactor surfaces, such as solvent cleaning, various hydraulic and mechanical reactor cleaners, and the like. See, for example, U.S. Pat. Nos. 3,645,452 and 3,741,808 on hydraulic reactor cleaners. In addition, various methods of coating the reactor surfaces prior to polymerization have been proposed. See, for example, U.S. Pat. Nos. 4,024,330; 4,024,301 and 4,081,248. These various methods and apparatus have done a more than acceptable job. However, the art continues to strive to find the ultimate in the prevention of polymer buildup, particularly, from an economic and environmental point of view.
While the various coating solutions heretofore proposed have been more than satisfactory in achieving the desired results, experience on a commercial scale has shown that more dilute coating solutions would be desirable in order to reduce costs and more importantly, to reduce the color of said solutions, since most all of them are colored. Due to this color, there is a tendency, on occasion, for some of the polymer particles being formed during the polymerization reaction in the presence of the coating on the inner surfaces of the polymerizer to become discolored which, of course, is undesirable and to be avoided, if possible. It should be pointed out, however, that the effectiveness of such coating solutions in reducing, and substantially eliminating polymer buildup is not affected by such discoloration problems. However, work continues to find the ultimate in a reactor coating and particularly one which eliminates the potential discoloration problem.